My son's home from school when I see this. We try out a few examples, starting with those in the videos. Then we do a few more...and then we do: 13 x 23. I'm

My son's home from school when I see this. We try out a few examples, starting with those in the videos. Then we do a few more...and then we do: 13 x 23. I'm obviously missing something hidden in this method, as our result, 416...fail ;(